EP3013875B1

EP3013875B1 - A high-temperature high-pressure (hthp) stable synthetic polymer for water based oil-well servicing fluids

Info

Publication number: EP3013875B1
Application number: EP14817148.1A
Authority: EP
Inventors: Janice Jianzhao Wang; Mohand Melbouci; Jeffrey Lynn; Cuiyue Lei; Musa M. OSAMA
Original assignee: ISP Investments LLC
Current assignee: ISP Investments LLC
Priority date: 2013-06-27
Filing date: 2014-04-28
Publication date: 2020-02-26
Anticipated expiration: 2034-04-28
Also published as: US20160272868A1; EP3013875A4; CY1123205T1; EP3013875A1; DK3013875T3; MX2015017707A; US10202533B2; SA518391099B1; SA515370316B1; WO2014209485A1

Description

FIELD OF THE INVENTION

The present application relates to oil and gas applications, and more particularly, to water based High-Temperature-High-Pressure (HTHP) drilling fluid compositions, process for preparing and method of use.

BACKGROUND OF THE INVENTION

As more and more challenging conditions are encountered in oilfield drilling operations, there is a need for high-performance rheology modifiers used in water-based drilling fluids. The enhanced performance of the drilling fluids, especially, the High-Temperature-High-Pressure (HTHP) compatibility will allow faster and safer drilling operations. A rheology modifier is a critical component in water-based drilling fluids to ensure a proper rheology profile which performs specific functions such as suspending weighting agents and hole-cleaning. Xanthan Gum is the most commonly used rheology modifier in water-based drilling fluids. The xanthan gum was known to start losing rheological properties at above 148.89°C [300°F], so it is not suitable for HTHP based drilling operations. Therefore, a desired rheology modifier should possess similar rheological properties, for example, highly shear thinning with enhanced thermal stability. These enhanced properties will allow successful drilling operations under HTHP conditions. Therefore, the development of such HTHP based rheology modifier is critically important to the oil and energy based industries where drilling plays a vital role. The HTHP compatible water-based drilling fluid will allow more environmental friendly drilling operations in a safe and efficient manner. Therefore, without a high performance rheology modifier, such drilling operations under HTHP conditions are extremely challenging.
US 6 030 928 discloses a process comprising forming a drilling fluid comprising water, a clay and a polymer comprising a vinyl lactam monomer, an unsaturated carboxylic acid monomer, an unsaturated amide monomer and a vinyl-containing sulfonate monomer, and circulating the drilling fluid during drilling a well under hostile temperatures and divalent ion concentrations. Said document furthermore discloses a drilling fluid comprising the polymer and at least 30% of a weighting agent. The fluid is used in a saline environment.
US Patent No. 7,205,271 assigned to ISP Investments Inc. discloses a rheology modifier/hair styling resin consisting of a crosslinked, linear poly(vinyl amide/polymerizable carboxylic acid) copolymer having a composition, by weight, of 25 to 75% of a vinyl amide monomer selected from vinyl pyrrolidone, vinyl caprolactam, N-vinyl formamide, N-vinylacetamide, N-vinyl-N-methylacetamide and mixtures thereof, and 25 to 75% of a polymerizable carboxylic acid monomer selected from (meth)acrylic acid, crotonic acid, itaconic acid, maleic acid and mixtures thereof, and a crosslinker in an amount of 0.5 to 2% based on weight of total monomers, which is characterized by an aqueous solution having a viscosity of 55000 mPas [55,000 cps] at a pH of 9 (BrookfieldRVT, T-bar C@ 10 RPM, 60 sec., 1% resin solids in water).
US Publication No. 20110218295 assigned to BASF SE discloses a new anionic associative rheology modifiers comprising as polymerized units (a) 25 to 85% by weight of acrylic acid (AA), (b) 10 to 60% by weight of N-vinyl pyrrolidone (VP), (c) 0.5 to 10% by weight of at least one cationic monomer, (d) 1 to 6% by weight of at least one of compounds (d1) or (d2).
US Patent No. 5,211,858 assigned to Union Oil Company of California discloses a method for inhibiting the migration of a hazardous acid plume through a subterranean stratum, the method comprising the step of injecting into at least a portion of the acid plume a slug of a composition capable of forming a gel, the composition comprising: (a) a crosslinkable polymer; and (b) a lanthanide, wherein the crosslinkable polymer is selected from the group consisting of polyacrylamide and copolymers of acrylamide and (A) acrylic acid (B) Vinylpyrrolidone, (C) sodium 2-acrylamido-2-methylpropane sulfonate, and (D) mixtures of (A), (B), and (C).
US Patent No. 5393810A assigned to Halliburton Company disclose a compositions and methods which provide improved viscosity reduction of crosslinked hydratable polymer treating fluids in the presence of uncured resin-coated proppants. The uncured resins are generally uncured phenolic or furan resins. The breaker comprises an oxidizing agent to which is added a sequestering agent comprising a copolymer of vinylpyrrolidone and acrylic acid to sequester at least a portion of any phenolic extracts from said resin that may be present in said treating fluid from contact with the uncured resin.
US Publication No. 20080193395 assigned to BEIERSDORF AG disclose a cosmetic preparation containing (a) one or more water-soluble UV photo protective filters selected from the group of the compounds 2-phenylbenzimidazole-5-sulfonic acid and the sodium, potassium and triethanolammonium salts thereof as well as phenylene-1,4-bis-(2-benzimidazyl)-3,3'-5,5'-tetrasulfonic acid and the sodium, potassium and triethanolammonium salts thereof, (b) a copolymer of vinylpyrrolidone (VP) and acrylic acid (AA).
In view of the foregoing, it is an object of the present application to provide high performance rheology modifiers which is (i) capable retaining its original rheological properties even at high temperatures i.e. beyond 148.89°C [300°F]; (ii) compatible for water based oil field drilling operations under HTHP conditions; and (iii) capable to providing highly shear thinning property with enhanced thermal stability.
Surprisingly, we have found that the use of crosslinked, linear poly(vinyl amide/polymerizable carboxylic acid) copolymer is able to provide required high performance rheological properties which are suitable for HTHP water based oil-well servicing fluids. Such copolymer may be used alone or in combination with other at least one HTHP or Non-HTHP based Rheology Modifiers (RMs), Fluid Loss Additives (FLA's) and/or dispersants that are known in the prior arts.

SUMMARY OF THE INVENTION

The primary objective of the present application is to provide a stable water based High-Temperature-High-Pressure (HTHP) and/or Non-HTHP based drilling fluid composition comprising a new copolymer for oil and/or gas applications, and wherein, said composition consists of (i) a crosslinked, linear of poly(vinyl amide/polymerizable carboxylic acid) copolymer, having a composition, by weight, of 25-75 wt. % of a vinyl amide monomer selected from vinyl pyrrolidone, vinyl caprolactam, N-vinyl-N-methylacetamide and mixtures thereof, and 25-75 wt. % of a polymerizable carboxylic acid monomer selected from acrylic acid, (meth)acrylic acid, crotonic acid, itaconic acid, maleic acid and mixture thereof; and (ii) a crosslinker in an amount of 0.01-5% based on weight of total monomers; and wherein, the crosslinked, linear poly(vinyl amide/polymerizable carboxylic acid) copolymer can be characterized by an aqueous solution having a viscosity of about 30000 to 90000 mPas [30,000 to 90,000 cps] at pH 9, and wherein, the Brookfield RVT, T-Bar C @ RPM, 60 Sec, 1% resin solids in water.
Yet another aspect of the present application provides that the crosslinked, linear copolymer of poly(vinyl amide/polymerizable carboxylic acid) can be used in oil and gas application as rheology modifier/thickener/suspension agent for drilling/drill-in fluids, completion fluids, work-over fluids, packer fluids, cementing suspending aid, friction reducer in oil-well stimulation fluid, shale swell inhibitor/clay stabilizer, fluid loss additive, viscosifier of water based drilling fluids, filtration control, viscosifier for oil-well stimulation, and/or polymer flooding for enhanced oil recovery.
One another aspect of the present application is to provide a stable water based High-Temperature-High-Pressure (HTHP) and/or Non-HTHP drilling fluid comprising: (i) fresh water or brine solution as base fluid, (ii) about 1.43 kg/m³ [0.5 ppb] to about 28.50 kg/m³ [10 ppb] of a crosslinked or linear poly(vinyl amide/polymerizable carboxylic acid) copolymer as rheology modifier; (iii) about 0 to about 71.25 kg/m³ [0 to about 25 ppb] of a dual-functional tetrapolymer of (AM/AMPS/AHPS/AA)that can function as both HT rheology modifier and HTHP based Fluid Loss Additive (FLA); (iv) about 0 to 71.25 kg/m³ [0 to 25 ppb] of HTHP or non-HTHP based Fluid loss additives, (v) about 228.00 kg/m³ [80 ppb] to about 1140.00 kg/m³ [400 ppb] of weighting agents; (vi) optionally about 0 kg/m³ [0 ppb] to about 85.50 kg/m³ [30 ppb] of drilling solids; and (vii) optionally, about 0 to about 85.50 kg/m³ [0 to about 30 ppb] of at least one dispersing agents.
Another aspect of the present application is to provide a stable water based High-Temperature-High-Pressure (HTHP) and/or Non-HTHP completion fluid, having a density of from about 994.56 to 2516.35 kg/m³ [8.3 to 21.0 ppg], comprising: (i) brine based fluids; (ii) about 1.43 kg/m³ [0.5 ppb] to about 28.50 kg/m³ [10 ppb] of a crosslinked, linear poly(vinyl amide/polymerizable carboxylic acid) copolymer based rheology modifier; (iii) optionally about 0 to 71.25 kg/m³ [0 to 25 ppb] of a dual-functional polymer of poly(AM/AMPS/AHPS/AA); and (iv) optionally about 14.25 kg/m³ to 285.00 kg/m³ [5 ppb to 100 ppb] bridging agent.
A further aspect of the present application is to provide a stable water based High-Temperature-High-Pressure (HTHP) and/or Non-HTHP drill-in fluids composition, having a density of from about 994.56 to about 2516.35 kg/m³ [8.3 to about 21.0 ppg], comprising: (i) brine based fluids; (ii) about 1.43 kg/m³ [0.5 ppb] to about 28.50 kg/m³ [10 ppb] of a crosslinked, linear poly(vinyl amide/polymerizable carboxylic acid) copolymer based rheology modifiers; (iii) about 0-71.25 kg/m³ [0-25 ppb] of Fluid Loss additives, (iv) optionally about 0 to 71.25 kg/m³ [0 to 25 ppb] of a dual-functional polymer additive of poly(AM/AMPS/AHPS/AA); and (v) about 14.25 kg/m³ [5 ppb] to about 285.00 kg/m³ [100 ppb] of bridging agents such as CaCO₃, orsized salts.

DETAILED DESCRIPTION OF THE INVENTION

While this specification concludes with claims particularly pointing out and distinctly claiming that which is regarded as the invention it is anticipated that the invention can be more readily understood through reading the following detailed description of the invention and study of the included examples.
By the term "comprising" herein is meant that various optional, compatible components can be used in the compositions herein, provided that the important ingredients are present in the suitable form and concentrations. The term "comprising" thus encompasses and includes the more restrictive terms "consisting of' and "consisting essentially of' which can be used to characterize the essential ingredients such as fresh water, brine, rheology modifier (RM), HTHP or non-HTHP based fluid loss additive (FLA), drilling solid, weighting agent of the present application.
All references to singular characteristics or limitations of the present invention shall include the corresponding plural characteristic or limitation, and vice-versa, unless otherwise specified or dearly implied to the contrary by the context in which the reference is made.
As used herein, the words "preferred," "preferably" and variants refer to embodiments of the invention that afford certain benefits, under certain circumstances. However, other embodiments may also be preferred, under the same or other circumstances. Furthermore, the recitation of one or more preferred embodiments does not imply that other embodiments are not useful, and is not intended to exclude other embodiments from the scope of the invention.
References herein to "one embodiment," "one aspect", "one version" or "one objective" of the invention include one or more such embodiment, aspect, version or objective, unless the context clearly dictates otherwise.
The unit "pounds per barrel" can also be specified as "ppb" or "lbm/bbl", and wherein one lbm/bbl or ppb is the equivalent of 0.454 kg [one pound] of additive in 0.159 m³ [42 US gallons] of mud. The "m" is used to denote mass to avoid possible confusion with pounds force (denoted by "lbf'). In SI units, the conversion factor is one pound per barrel equals 2.85 kilograms per cubic meter. For example, 10 lbm/bbl= 28.5 kg/m³.
The term "crosslinked" herein refers to a composition containing intra-molecular and/or intermolecular crosslinks, whether arising through a covalent or non-covalent bonding. "Non-covalent" bonding includes both hydrogen bonding and electrostatic (ionic) bonding.
The term "monomer" refers to the repeat units that comprise a polymer. A monomer is a compound that chemically bonds to other molecules, including other monomers, to form a polymer.
The term "polymer" refers to both linear and branched polymers derived from one or more monomer units, which may or may not be crosslinked, or grafted. Non-limiting examples of polymers include copolymers, terpolymers, tetramers, and the like, wherein the polymer is random, block, or alternating polymer.
The present application is directed to a thermally-stable polymer suitable for use under HTHP conditions. HTHP refers generally to wells that are hotter or at higher pressure than most wells. In accordance with some aspects, HTHP may refer to a well having an undisturbed bottom-hole temperature of greater than 148.89°C [300°F] and a bottom-hole pressure of at least 34.47 MPa [5000 psi].
What is described here is a stable water based High-Temperature-High-Pressure (HTHP) and/or Non-HTHP crosslinked, linear copolymer for oil and gas applications consisting of (i) a crosslinked, linear poly(vinyl amide/polymerizable carboxylic acid) copolymer, having a composition, by weight, of 25-75 wt. % of a vinyl amide monomer selected from vinyl pyrrolidone, vinyl caprolactam, N-vinyl-N-methylacetamide and mixtures thereof, and 25-75 wt. % of a polymerizable carboxylic acid monomer selected from acrylic acid, (meth)acrylic acid, crotonic acid, itaconic acid, maleic acid and mixture thereof; and (ii) a crosslinker in an amount of 0.01-5% based on weight of total monomers; and wherein, the copolymer is characterized by an aqueous solution having a viscosity of 30000 to 90000 mPas [30,000 to 90,000cps] at pH of 9 and wherein, the Brookfield RVT, T-bar C @10 RPM, 60 sec, 1% resin solids in water.
The vinyl amide based monomer of the present applicationis selected from vinyl pyrrolidone, vinyl caprolactam, N-vinyl-N-methylacetamide and mixtures thereof, preferably vinyl lactam based monomer such as vinyl pyrrolidone.
Other vinyl amide and/or vinyl lactam based monomers for the present application would include but not limited to N-vinyl formamide, N-vinyl-N-methyl formamide, N-vinyl-N-ethyl formamide, N-vinyl-N-(n-propyl)formamide, N-vinyl-N-isopropyl formamide, N-vinyl acetamide, N-vinyl-N-ethyl acetamide, N- vinyl-N-(n-propyl)acetamide, N-vinyl-N-isopropyl acetamide, N-vinyl propionamide, N-vinyl- N-methyl propionamide, N-vinyl-N-ethyl propionamide, N-vinyl-N-(n-propyl)propionamide, N- vinyl-N-isopropyl propionamide, N-vinylbutanamide, N-vinyl-N-methyl butanamide, N-vinyl-N- ethyl butanamide, N-vinyl-N-(n-propyl)butanamide, N-vinyl-N-isopropyl butanamide, N-vinyl-2-pyrrolidone, N-vinyl-2-piperidone, N-vinyl-2-caprolactam, N-vinyl-3-methyl-2-pyrrolidone, N-vinyl-3 -methyl-2-piperidone, N-vinyl-3-methyl-2-caprolactam, N-vinyl-4-methyl-2-pyrrolidone, N-vinyl-4-methyl-2-caprolactam, N-vinyl-5-methyl-2-pyrrolidone, N-vinyl-5-methyl-2-piperidone, vinyl-5,5-dimethyl-2-pyrrolidone, N-vinyl-3,3,5-trimethyl-2-pyrrolidone,
N-vinyl-5-methyl-5-ethyl-2-pyrrolidone, N-vinyl-3,4,5-trimethyl-3-ethyl-2-pyrrolidone, N-vinyl-6-methyl-2-piperidone, N-vinyl-6-ethyl-2-piperidone, N-vinyl-3,5-dimethyl-2-piperidone, N-vinyl-4,4-dimethyl-2-piperidone, N-vinyl-7-methyl-2-caprolactam, N-vinyl-7-ethyl-2-caprolactam, N-vinyl-3,5-dimethyl-2-caprolactam, N-vinyl-4,6-dimethyl-2-caprolactam, N-vinyl-3,5,7-trimethyl-2-caprolactam, derivatives thereof, and blends thereof. Particularly useful N-vinyl lactams include N-vinyl-2-pyrrolidone, N-vinyl-2-piperidone and N-vinyl-2-caprolactam, derivatives thereof, and blends thereof.
The polymerizable carboxylic acid of the present application is selected from acrylic acid, (meth)-acrylic acid, crotonic acid, itaconic acid, maleic acid and mixtures thereof, preferably acrylic acid (AA).
The crosslinker for preparing crosslinked copolymers of the present application is required to have at least two free radically polymerizable groups in the molecule and is selected from the group consisting of Pentaerythritol-di-allylether, Pentaerythritol-di-(meth)acrylate, Pentaerythritol tri(meth)acrylate, Pentaerythritol- tetra-(meth)acrylate, Divinylimidazolidone (DVI), N,N',N"-triallyl-triazine-trione, Methyene- bis-acryamide, Methylene-bis-(meth)acrylamide, Triallyl-amine, Triallylglucose, Ethyleneglycol-di-(meth)acrylate, Diethyleneglycol-di-(meth)acrylate, Triethyleneglycol-di- (meth)acrylate, Tetraethyleneglycol-di-(meth)acrylate, Polyethyleneglycol-di-(meth)acrylate, 1- vinyl-3-(E)-ethylidene-pyrrolidone (EVP), Allyl methacrylamide, allyl glycidyl ether, glycidyl acrylate, hydroxyacrylamide and Divinylbenzene.
Other crosslinking agents for the present application are selected from the group consisting of melamines, formaldehyde, chromates, polyfunctional silanes, zirconates, borates, polyfunctional acids, poly functional amines, alkylamino derivatives of methacrylic acids, alkylamino derivatives of methacrylamides, acid anhydrides, unsaturated aliphatic acids, vinyl derivatives, silanes, oxirane based glycidyl ethers, glycidyl acrylates, epoxy compounds, acrylic anhydrides, oxazoline derivatives, benzoxazine compounds, aziridine compounds, aziridine derivatives of methacrylates, isocyano derivatives of methacrylate, carbamic acid derivatives, sulfonate ester compounds, sulfonyl compounds, carbodiimide compounds, allyl compounds alone or in combination.
The copolymer according to the present application may readily be synthesized by the procedures that are known to a person skilled in the relevant art, and such free radical polymerization methods include but not limited to precipitation polymerization, inverse emulsion polymerization, gel polymerization, dispersion polymerization, solution polymerization, emulsion polymerization, bulk polymerization, suspension polymerization, or Liquid dispersion polymerization (LDP). The polymers can also be made through ionic polymerization.
Other preferred polymerization techniques employed to carry out the said copolymer of present application is duly disclosed in (1) "Principles of Polymerization" 4th edition, 2004, Wiley by George Odian and (2) WO2012061147A1 assigned to ISP Investments Inc.. Further, the polymerization of copolymer of the present application optionally may require a suitable catalysts or initiators, stabilizers, salts, pH adjusting agents, co-dispersants, thickeners, solvents, acidic agents, basic agents, and/or photoinitiators depends on type of polymerization technique being employed, and one skilled in the art can easily derive such information from the relevant literature known in the prior-art or from "Principles of Polymerization" 4th edition, 2004, Wiley by George Odian.
The polymers of the present application is thermally-stable, in particular, to a polymer suitable for use under HTHP conditions, and wherein HTHP refers generally to wells that are hotter or at higher pressure than most wells. In accordance with some aspects, HTHP may refer to a well having an undisturbed bottom-hole temperature of greater than 148.89°C [300F] and a bottom-hole pressure of greater than 34.47 MPa [5000 psi].
According to one embodiment of the present application, the polymer can also be employed in Non-HTHP conditions as well, and wherein, the Non-HTHP condition would include temperature ranging from ambient to about 121.11°C [250°F].
A particularly preferred embodiment of the present application (not literally claimed) provides a process for preparing crosslinked poly(vinyl amide/polymerizable carboxylic acid) copolymer of the present application comprising precipitation polymerization, by wt. 5-50%, preferably 10-40%, of a mixture of a vinyl amide, a polymerizable carboxylic acid and a crosslinker, in the presence of 50-95%, preferably 60-90%, of a non-polar, removable organic solvent, and 0.05-5%, preferably 0.1-1%, of a free radical initiator, based on total weight of monomers. The copolymer of the present application is made according to US Patent No. 7,205,271 assigned to ISP Investments Inc..
Another important embodiment of the present application provides a stable water based High-Temperature-High-Pressure (HTHP) and/or Non-HTHP drilling fluid comprising: (i) fresh water and/or brine solution as a base fluid, (ii) about 1.43 kg/m³ [0.5 ppb] to about 28.50 kg/m³ [10 ppb] of a crosslinked, linear poly(vinyl amide/polymerizable carboxylic acid) copolymer as a rheology modifier; (iii) about 0 to about 71.25 kg/m³ [25 ppb] of a dual-functional polymer, (iv) about 0 to about 71.25 kg/m³ [25 ppb] of HTHP or non-HTHP based FLAs; (v) about 228.00 kg/m³ [80 ppb] to about 1140.00 kg/m³ [400 ppb] of weighting agents; (iv) optionally about 0 kg/m³ [0 ppb] to about 85.50 kg/m³ [30 ppb] of drilling solids; and (vii) optionally about 0 kg/m³ [0 ppb] to about 85.50 kg/m³ [30 ppb] of at least one dispersing agents.
The preferred copolymer for the above said stable water based High-Temperature-High-Pressure (HTHP) and/or Non-HTHP drilling fluid is a crosslinked, linear copolymer of poly(vinylpyrrolidone/acrylic acid) or Poly(VP/AA), and wherein, the suitable amount of Poly(VP/AA), a desired HT Rheology Modifier of the present application is in the range of from about 1.43 kg/m³ to 28.50 kg/m³ [0.5 ppb to 10 ppb].
According to one preferred embodiment of the present application a dual-functional polymer which is provided is capable to functioning as a Rheology Modifier (RM) and/or Fluid Loss Additive (FLA), for the present application, said dual-functional polymer is selected from the group consisting of a tetrapolymer obtained by polymerizing (i) an acrylamide (AM) or a substituted acrylamide selected from the group consisting of N-methacrylamide, N-isopropylacrylamide, N-butylacrylamide, N,N-dimethylacrylamide, or N-hydroxymethylacrylamide; (ii) a monomer containing sulfonate functionality is 2-acrylamido-2-methylpropanesulfonic acid (AMPS); (iii) a substituted allyl alkylene ether compound is selected from the group consisting of 3-allyloxy-hydroxy-propanephosphate, 3-allyloxy-hydroxy-propanesulfonate, and 3-allyloxy-hydroxy-propanephosphite; and, (iv) a monomer containing carboxylic acid functionality is selected from the group consisting of acrylic acid, methacrylic acid, maleic acid or anhydride, itaconic acid, crotonic acid, fumaric acid, and citraconic acid; and a crosslinker in an amount of 0.1-5% based on weight of total monomers.
The dual-functional polymer of the present application is a crosslinked polymer of (i) an acrylamide (AM); 2-acrylamido-2-methylpropanesulfonic acid (AMPS); (iii) 3-allyloxy-hydroxy-propanesulfonate (AHPS); and, (iv) acrylic acid (AA); and wherein, N,N-methylene-bis-acrylamide is a preferred crosslinker.
According to one aspect of the present application, the drilling fluid composition can advantageously employ any appropriate additional Rheology Modifiers (RMs) and Fluid Loss Additives (FLAs) along with claimed Rheology Modifiers (RMs) and Fluid Loss Additives (FLAs) of the present application. The additional Rheology Modifiers (RMs) and Fluid Loss Additives (FLAs) may be selected from the prior arts that are known for a person skilled in the relevant art.
Other suitable Rheology Modifier of the present application would include but not limited to a terpolymer of acrylamide (AM)/2-acrylamido-2-methyl propanesulfonic acid (AMPS)/hydrophobe; a terpolymer of acrylamide (AM)/2-acrylamido-2-methyl propanesulfonic acid (AMPS)/C_12-25 alkyl acrylate; carboxymethyl cellulose, hydroxyethylcellulose, carboxymethylhydroxyethyl cellulose, sulphoethylcellulose; starch derivatives/crosslinked starch derivatives including carboxymethyl starch, hydroxyethylstarch, hydroxypropyl starch; bacterial gums including xanthan, welan, diutan, succinoglycan, scleroglucan, dextran, pullulan; plant derived gums such as guar gum, locust-bean gum, tara gum and their derivatives, polyanionic cellulose (PAC), hydroxyethyl cellulose (HEC), Hydroxypropyl cellulose (HPC), carboxymethyl hydroxyethyl cellulose (CMHEC), carboxymethyl cellulose (CMC), xanthan gum, guar gum, and mixtures thereof.
Suitable additional Fluid Loss Additives of the present application would include but not limited to Polydrill, Alcomer 242 and Alcomer 507 from BASF, KEM-SEAL from Baker Hughes, DURALON from MI-Swaco, DRISCAL D from Drilling Specialties, Hostadrill from Clariant, Therma-chek from Halliburton, terpolymer of acrylamide (AM)/2-acrylamido-2-methyl propanesulfonic acid (AMPS)/cationic monomers, carboxymethyl cellulose, carboxyethyl cellulose, lignite, xanthan gum, starch, , hydroxy methyl cellulose, hydroxy ethyl cellulose, guar gum, hydroxy propyl guar, hydroxy ethyl guar, and mixtures thereof.
Additional dual-functional polymer of the present application is vinylamide/vinyl sulfonic acid copolymer, e.g. Hostadrill (Clariant) which is capable of controlling down-hole filtration and their rheology properties in water based drilling applications, completion and workover fluids at an elevated temperature conditions.
The required amount of FLA for the desired composition of the present application is in the range of from about 0 kg/m³ [0 ppb] to about 14.25 kg/m³ [5 ppb]; about 14.25 kg/m³ [5 ppb] to about 28.50 kg/m³ [10 ppb]; about 28.50 kg/m³ [10 ppb] to about 42.75 kg/m³ [15 ppb]; about 42.75 kg/m³ [15 ppb] to about 57.00 kg/m³ [20 ppb]; and about 57.00 kg/m³ [20 ppb] to about 71.25 kg/m³ [25 ppb].
The stable water based high-temperature high-pressure (HTHP) and Non-HTHP drilling fluid of the present application comprises at least one weighting agent to provide the increased density to the composition. The weighting agent is primarily used to increase the density of fluids and control the fluid pressure to prevent blowout.
It is contemplated to employ a substance that is denser than water and does not adversely affect other properties of the mud composition can be added to raise the density to the desired level. The solubility of salts limits their range of usefulness, and there are other limitations associated with the use such systems. Therefore, various finely-ground solid materials can be used as a weighting agent. Several factors in addition to chemical inertness and specific gravity affect the use of a substance as a weighting material. Firstly, the substance should be available in large quantities. Secondly, it should easily be grounded to the preferred particle size distribution, having relatively non-abrasive nature. It should also be moderate in cost, and not injurious or objectionable to the drilling crew or the surroundings.
In an exemplary embodiment, the weighting agent may be selected from the group including but not limited to Galena, barite, hematite, illmenite, calcite, dolomite, siderite, Celestite magnetite, iron oxide, and mixtures thereof. The suitable ranges of the weighting agents for the present application are used in an amount required to achieve the density of 994.56 to about 2516.35 kg/m³ [8.3 to 21.0 ppg].
In a different embodiment, the aqueous drilling fluid composition of the present application employs either (i) fresh water or (ii) a suitable brine solution as a base fluid during drilling operations. The drilling fluid composition of the present application may also comprise seawater or a solution of a salt or a solution of a combination of salts required thereof.
Generally, the brine solution is present in an amount to achieve the density of from about 994.56 to about 2516.35 kg/m³ [8.3 to 21.0 ppg]. The brine solution may be an aqueous solution of one or more density- increasing water-soluble salt. The density increasing water-soluble salt may be selected from the group consisting of alkali metal halides (for example, sodium chloride, sodium bromide, potassium chloride, potassium bromide, magnesium chloride, ammonium chloride) alkali metal carboxylates (for example, sodium formate, potassium formate, caesium formate, sodium acetate, potassium acetate or caesium acetate), sodium carbonate, potassium carbonate, alkaline earth metal halides (for example, calcium chloride and calcium bromide), and zinc halide salts (zinc chloride, zinc bromide) and mixtures thereof. The salt for preparing the brine of present application is selected from the group consisting of sodium chloride, potassium chloride, calcium chloride, magnesium chloride, ammonium chloride, zinc chloride, sodium bromide, calcium bromide, zinc bromide, potassium formate, cesium formate, sodium formate and mixtures thereof.
According to another embodiment of the present application, at least one drilling solid agent is employed to provide enhanced viscosity, density, gel strength to the drilling fluid or mud, and thus gives it good suspension capacity to oppose any settling of the cuttings.
Examples of suitable drilling solid may be selected from the group consisting of but not limited to clays bentonite, attapulgite, hectorite, sepiolite, and the synthetic minerals Laponite™ (a synthetic hectorite ex Rockwood Additives Limited) and mixed metal hydroxides. Other clays which may be present in the fluids include kaolinite and illite which can be contaminants arising from drilled shale formations. Some of the shale cuttings inevitably become dispersed in a wellbore fluid as fine illite and kaolinite clay particles. The preferred drilling solid of the present application is finely divided clay particles selected from the group consisting of bentonite, sodium bentonite, attapulgite, sepiolite, saponite, hectorite and mixtures thereof. Suitable range of drilling solids for the present application is in the range of from about 0 to about 85.50 kg/m³ [30 ppb] of the total composition. Other preferred range of drilling solid would include but not limited to 0 to 42.75 kg/m³ [15 ppb].
According to another embodiment of the present application, it is contemplated to employ optionally a dispersing agent to achieve desired rheological quality of the drilling fluid before aging (BHR). Such dispersing agents or dispersants may be selected from the prior-arts of related field of applications that are known for a person skilled in the art. However, the preferred dispersing agent would include but not limited to plant tannins, lignites, lignosulfonates, polyphosphates, phosphonates, polyacrylates, low molecular weight cellulosic derivatives, polymaleates, poly(maleate/allylsulfonate) and the like. The most preferred dispersing agent of the present application is poly(maleate/allylsulfonate) based polymer.
The water based drilling fluid of the present application may comprise additional additives for improving the performance of drilling operations with respect to one or more properties. Examples of such additional additives may be selected from the group including but not limited to bactericides, detergents and emulsifiers, solid and liquid lubricants, gas-hydrate inhibitors, corrosion inhibitors, defoaming agents, scale inhibitors, enzymes, oxidizing polymer- breakers, emulsified hydrophobic liquids such as oils, acid gas-scavengers (such as hydrogen sulfide scavengers), thinners (such as lignosulfonates), demulsifying agents and surfactants designed to assist the clean-up of invaded fluid from producing formations, polymeric additives, dispersants, shale stabilizers or inhibitors, pH controlling agents, wetting agents, biopolymers, pH controlling agents or mixture thereof. Preferred additives would include polymeric additives, filtration control additives, dispersants, shale stabilizers or inhibitors, clay swell inhibitors, pH controlling agents or buffers, emulsifiers, antifoaming agents, wetting agents, surfactants, corrosion inhibitors, lubricants, biocides or mixture thereof.
The desired copolymer of the present application is used in oil and gas application as rheology modifier/thickener/suspension agent for drilling/drill-in fluids, completion fluids, work-over fluids, packer fluids, cementing suspending aid, friction reducer in oil-well stimulation fluid, shale swell inhibitor/clay stabilizer, fluid loss additive, viscosifier of water based drilling fluids, filtration control, viscosifier for oil-well stimulation, and/or polymer flooding for enhanced oil recovery.
The water based drilling fluid of the present application is suitable for high-temperature high-pressure (HTHP) drilling operations having a temperature greater than (>) 148.89°C [300°F], and wherein, the Non-HTHP drilling operations having a temperature of ambient to about 121.11°C [250°F].
Suitable pH for these water based drilling fluid compositions of the present application is in the range of from about 6.0 to about 13.0.
One important embodiment (not literally claimed) of the present application provides a method for conducting HTHP aging test to evaluate high temperature thermal stability of Rheology Modifiers of the present application through dynamic or hot rolling conditions. The detailed experimental process comprises as follows: rheology measurements of the drilling fluids after preparation (BHR), and rheology measurements of the drilling fluids after static or hot-rolling (AHR) for 16 hours at test temperatures.
A very important embodiment of the present application provides a stable water based High-Temperature-High-Pressure (HTHP) and/or Non-HTHP drilling fluid comprising: (i) brine solutions and/or fresh water as base fluids, (ii) a rheology modifier consisting of (a) crosslinked, linear poly(vinyl pyrrolidone/acrylic acid) copolymer, having a composition, by weight, of 25-75 wt. %, and 25-75 wt. % of a acrylic acid monomer; and (b) a crosslinker in an amount of 0.1 to 5 wt% based on weight of total monomers; (iii) a dual-functional polymer consisting of (a) an acrylamide (AM); (b) 2-acrylamido-2-methylpropanesulfonic acid (AMPS); (c) 3-allyloxy-hydroxy-propanesulfonate (AHPS); and, (d) acrylic acid (AA); and wherein, N,N-methylene-bis-acrylamide is a crosslinker for the tetrapolymer; (iv) about 0 kg/m³ [0 ppb] to about 71.25 kg/m³ [25 ppb] of HTHP or non-HTHP based Fluid Loss Additives (FLA); (v) about 228.00 kg/m³ [80 ppb] to about 1140.00 kg/m³ [400 ppb] of weight agents; (vi) optionally about 0 kg/m³ [0 ppb] to about 85.50 kg/m³ [30 ppb] of drilling solids; and (vii) optionally about 0 kg/m³ [0 ppb] to about 85.50 kg/m³ [30 ppb] of at least one dispersing agents.
A particularly preferred embodiment of the present application provides a stable water based High-Temperature High-Pressure (HTHP) and/or Non-HTHP completion fluid, having a density of from about 994.56 to about 2516.35 kg/m³ [8.3 to 21.0 ppg], comprising: (i) brine based fluids; (ii) about 1.43 kg/m³ [0.5 ppb] to about 28.50 kg/m³ [10 ppb] of a crosslinked, linear poly(vinyl amide/polymerizable carboxylic acid) copolymer, a rheology modifier; (iii) optionally about 0 to 71.25 kg/m³ [25 ppb] of a dual-functional polymer of poly(AM/AMPS/AHPS/AA); and (iv) optionally about 14.25 to 285.00 kg/m³ [5 to 100 ppb] bridging agent.
Another preferred embodiment of the present application provides a stable water based High-Temperature High-Pressure (HTHP) and/or Non-HTHP drill-in fluids composition, having a density of from about 994.56 to about 2516.35 kg/m3 [8.3 to about 21.0 ppg], comprising: (i) brine based fluids; (ii) about 1.43 kg/m³ [0.5 ppb] to about 28.50 kg/m³ [10 ppb] of a crosslinked, linear poly(vinyl amide/polymerizable carboxylic acid) copolymer based a rheology modifiers; (iii) optionally about 0 to 71.25 kg/m³ [25 ppb] of a dual-functional polymer of poly(AM/AMPS/AHPS/AA); and (iv) about 14.25 kg/m³ [5 ppb] to about 285.00 kg/m³ [100 ppb] of bridging agents such as CaCO₃, or sized salts.
Accordingly, in a particularly useful embodiment (not literally claimed) of the present application there is provided a method of drilling a wellbore through a subterranean rock formation comprising (i) providing a drilling fluid composition of present application; (ii) pumping said drilling mud composition down tubing in the wellbore and through nozzles in a drilling bit attached to the bottom end of the tubing while rotating the bit to detach cuttings from the rock formation; and (iii) transporting the cuttings up the annulus between the tubing and the wellbore wall, the cuttings transport being facilitated by the flow of drilling fluid composition of the present application.
Another embodiment of the present application (not literally claimed) provides a method of completing a wellbore that penetrates through a porous and permeable subterranean rock formation comprising (i) providing a completion drilling fluid composition of present application; (ii) pumping said completion mud composition into the wellbore so that the formation fluid pressure and/or losses of completion fluid to the formation are controlled; and (iii) performing the operations required to complete the well.
In a different embodiment of the present application (not literally claimed), there is provided a method of fracturing a rock formation comprising injecting a fracturing fluid into an wellbore across the rock formation that is to be fractured wherein the fracturing fluid comprises the composition of present application; and maintaining the pressure of the fracturing fluid at above the fracture pressure of the formation whereby the fractures grow and the drilling fluid composition of present application assists the transport of the proppant particles along the fractures and reduces the rate of leak-off of the fluid into the rock formation.
Further, the present invention is illustrated in detail by way of the below given examples. The examples are given herein for illustration of the invention and are not intended to be limiting thereof.

EXAMPLE 1: Preparation of drilling mud compositions

A ∼ 1437.91 kg/m³ [12 ppg] drilling fluid formulation as described in Table 1 was made on a 600g scale containing weighting agents, a HT rheology modifier, a dual-functional polymer, and a sulfonate based polymer dispersant as shown in following Table 1. Sufficient mixing was required to facilitate dissolving of the polymer and avoid local viscosified agglomerates (fish eyes). The drilling fluids were allowed to agitate for 5 to 15 minutes between the addition of each component and with 30 to 50 minutes total for complete and homogenous mixing. Rheological properties were then measured on a Fann 35 before and after hot rolling (BHR and AHR) aging tests.
The 1437.91 kg/m³ [12 ppg] drilling fluid fluids were prepared from the formulation provided in Table 1 and hot rolled under N₂ pressure of 2.41 MPa [350 psi] for 204.44°C [400°F] for 16 hours aging. HTHP fluid loss tests on drilling fluid formulations were conducted in accordance with the procedures detailed in API RP 13B-1. BHR and AHR rheology results and HTHP Fluid loss control properties are provided in Tables 3 to 6.
The study of HT rheology modifier of this invention in 1437.91-1617.65 kg/m³ [12-13.5 ppg] drilling muds containing 156.75 kg/m³ [55 ppb] KCl and 14.25 kg/m³ [5 ppb] Bentonite demonstrated good rheology retention, with good mud suspension capability after aging (Table 1). The low end viscosities at 3/6 rpm are still high enough to suspend the mud weighting agents; the AHR YPs of 20s for both muds reveals that AHR muds possess good pumpablity while still maintaining good suspension capabilities.
The study of HT rheology modifier of this invention in 1437.91 kg/m³ [12 ppg] drilling muds containing 99.75 kg/m³ [35ppb] KCl showed good thermal stability with exceptional mud rheology retention of PV, YP and suspension capability (Table 2). The low end viscosities at 3/6 rpm are still high enough to suspend the mud weighting agents; the AHR YPs in the range of 10-30s for all three muds indicates that AHR muds possess good pumpability while still maintain good suspension capabilities.
The study of HT rheology modifiers of this invention in 1917.22 kg/m³ [16ppg] containing 99.75 kg/m³ [35ppb] KCl drilling fluid composition revealed good rheology retention with good mud suspension capability after aging. Also, demonstrated significantly better PV and YP results (Table 3). The low end viscosities at 3/6 rpm are still high enough to suspend the mud weighting agents; the AHR YPs in the range of 20-30s for all three muds indicates that AHR muds possess good pumpability while still maintain good suspension capabilities.
The study of HT rheology modifier of this invention in 1318.09 kg/m³ [11 ppg] drilling muds containing 99.75 kg/m³ [35 ppb] KCl and 14.25 kg/m³ [5 ppb] Bentonite showed better thermal stability with excellent mud rheology retention of PV, YP and suspension capability (Table 4). The low end viscosities at 3/6 rpm are still high enough to suspend the mud weighting agents; the AHR YPs in the range of 20-30s for all three muds indicates that AHR muds possess good pumpability while still maintain good suspension capabilities.
The study of HT rheology modifier of this invention in 1917.22 kg/m³ [16 ppg] drilling muds containing 99.75 kg/m³ [35 ppb] KCl and 14.25 kg/m³ [5 ppb] Bentonite demonstrated good AHR PV, YP and suspension capability (Table 5). The muds containing HT Rheology modifier, a dual-functional polymer and/or a sulphonate based dispersant. (Formulations 12443632 and 12443-63-3) showed good AHR rheology, indicating the good suspension capability and pumpablity.
The study of HT rheology modifier of this invention in saturated NaCl for drill-in and completion fluids composition exhibited excellent rheology retention and suspension capabilities with or without dual-functional polymer after hot-rolling aging at 148.89-204.44°C [300-400°F] (Table 6).

While this invention has been described in detail with reference to certain preferred embodiments, it should be appreciated that the present invention is not limited to those precise embodiments. Rather, in view of the present disclosure, which describes the current best mode for practicing the invention, many modifications and variations would present themselves to those skilled in the art without departing from the scope of this invention.

Table 1: Study of HT RM in 1437.91-1617.65 kg/m³ [12-13.5ppg] drilling fluid muds containing 156.75 kg/m³ [55 ppb] KCl + 14.25 kg/m³ [5ppb] Bentonite

Composition	Mixing time	12443-50-1	12443-48-2
Deionized water, ml	--	249	230
Pre-hydrated API non-treated Betonite (81.51 kg/m³ [28.6ppb]), kg/m³ [ppb]	5min	188.67 [66.20]	151.05 [53]
KCl, kg/m³ [ppb]	2min	156.75 [55]	156.75 [55]
NaOH, 50%, kg/m³ [ppb]	30sec	5.70 [2.0]	5.70 [2.0]
Poly(/VP/AA), kg/m³ [ppb]	10min	5.70 [2.0]	6.56 [2.3]
API Barite, kg/m³ [ppb]	10min	541.50 [190]	656.50 [320]
Aging Conditions		204.44°C [400F]/1 6hr hot rolling aging

Mud weight, kg/m³ [ppg]	1437.91 [12]			1617.65 [13.5]
Fann data @48.89°C [120F]	BHR	AHR	R* (%)	BHR	AHR	R* (%)
600 rpm	75	53	71	75	56	75
300 rpm	55	40	73	59	40	68
200 rpm	47	30	64	53	35	66
100 rpm	40	25	63	44	29	66
6 rpm	25	15	60	24	14	58
3 rpm	23	14	61	21	13	62
10s gel, kg/m² [lb/100 ft²]	1.12 [23]	0.63 [13]	2.78 [57]	0.98 [20]	0.59 [12]	2.93 [60]
PV, mPas [cps]	20 [20]	13 [13]	65 [65]	16 [16]	16 [16]	100 [100]
YP, kg/m² [lb/100 ft²]	1.71 [35]	1.32 [27]	3.76 [77]	2.10 [43]	1.17 [24]	2.73 [56]
pH value	11.6	8.5	--	10.3	8.5	--

R*: Retention (%)

Table 2: Study of HT RM in 1437.91 kg/m³ [12ppg] drilling muds containing 99.75 kg/m³ [35 ppb] KCl

Composition	Mixing time	12443-57-1	12443-58-1	12443-57-3
Deionized water, ml	--	289	289	289
KCl, kg/m³ [ppb]	2min	99.75 [35]	99.75 [35]	99.75 [35]
NaOH, 50%, kg/m³ [ppb]	30sec	8.55 [3.0]	8.55 [3.0]	8.55 [3.0]
AM/AMPS/AHPS/AH, kg/m³ [ppb]	10min	0	14.25 [5.0]	14.25 [5.0]
Poly(VP/AA), kg/m³ [ppb]	10min	7.13 [2.5]	14.25 [5.0]	12.26 [4.3]
Poly(maleate/allylsulfonate), 48%, kg/m³ [ppb]	5min	0	0	7.13 [2.5]
API Barite, kg/m³ [ppb]	10min	513 [180]	518 [180]	518 [180]
Aging Conditions		204.44°C [400°F]/16hr hot rolling aging

Mud weight, kg/m³ [ppg]	1437.91 [12]			1437.91 [12]			1437.91 [12]
Fann data @48.89°C [120F]	BHR	AHR	R* (%)	BHR	AHR	R* (%)	BHR	AHR	R* (%)
600 rpm	60	57	95	105	80	77	100	74	74
300 rpm	40	37	93	82	57	70	70	52	74
200 rpm	32	30	94	66	42	64	59	42	71
100 rpm	27	22	81	48	33	69	42	30	71
6 rpm	17	9	53	22	17	77	20	14	70
3 rpm	16	8	50	20	15	75	18	13	72
10s gel, kg/m² [lb/100 ft²]	0.73 [15]	0.39 [8]	2.59 [53]	1.07 [22]	0.78 [16]	3.56 [73]	0.88 [18]	0.63 [13]	3.51 [72]
PV, mPas [cps]	20 [20]	20 [20]	100 [100]	23 [23]	23 [23]	100 [100]	30 [30]	22 [22]	73 [73]
YP, kg/m² [lb/100 ft²]	0.98 [20]	0.83 [17]	4.15 [85]	2.88 [59]	1.66 [34]	2.88 [59]	1.95 [40]	1.46 [30]	3.66 [75]
pH value	11.9	10.6	--	9.4	8.5	--	11.0	8.8	--

R*: Retention (%)

Table 3: Study of HT RM in 1917.22 kg/m³ [16ppg] drilling muds containing 99.75 kg/m³ [35ppb] KCl

Composition	Mixing time	12443-58-2	12443-60-4	12443-60-5
Deionized water, ml	--	237	237	237
KCl, kg/m³ [ppb]	2min	99.75 [35]	99.75 [35]	99.75 [35]
NaOH, 50%, kg/m³ [ppb]	30sec	8.55 [3.0]	8.55 [3.0]	8.55 [3.0]
Poly(VP/AA), kg/m³ [ppb]	10min	6.56 [2.3]	6.27 [2.2]	6.27 [2.2]
Tetrapolymer of AM/AMPS/AHPS/AA, kg/m³ [ppb]	10min	0	8.55 [3.0]	8.55 [3.0]
Poly(maleate/allylsulfonate), 48%, kg/m³ [ppb]	5min	0	0	8.55 [3.0]
API Barite, kg/m³ [ppb]	10min	940.50 [330]	940.50 [330]	940.50 [330]
Aging Conditions		204.44°C [400°F]/16hr hot rolling aging

Mud weight, kg/m³ [ppg]	1917.22 [16]			1917.22 [16]			1917.22 [16]
Fann data @48.89°C [120F]	BHR	AHR	R* (%)	BHR	AHR	R* (%)	BHR	AHR	R* (%)
600 rpm	97	81	84	80	76	95	74	68	92
300 rpm	77	57	74	55	51	93	51	49	96
200 rpm	67	47	70	42	40	95	43	39	91
100 rpm	55	34	62	30	27	90	33	29	88
6 rpm	35	15	43	18	9	50	19	12	63
3 rpm	34	13	38	16	7	44	18	11	61
10s gel, kg/m² [lb/100 ft²]	1.71 [35]	0.63 [13]	1.81 [37]	0.78 [16]	0.32 [6.5]	2.00 [41]	0.88 [18]	0.49 [10]	2.73 [56]
PV, mPas [cps]	20 [20]	24 [24]	120 [120]	25 [25]	25 [25]	100 [100]	23 [23]	19 [19]	83 [83]
YP, kg/m² [lb/100 ft2]	2.78 [57]	1.61 [33]	2.83 [58]	1.46 [30]	1.27 [26]	4.25 [87]	1.37 [28]	1.46 [30]	5.22 [107]
pH value	12.1	9.2	--	12.2	9.4	--	12.2	9.8	--

R*: Retention (%)

Table 4: Study of HT RM in 1318.09 kg/m³ [11ppg] drilling muds containing 99.75 kg/m³ [35ppb] KCl and 14.25 kg/m³ [5ppb] Bentonite

Composition	Mixing time	12443-61-3	12443-61-4	12443-61-5
Deionized water, ml	--	289	289	289
Pre-hydrated API Non-treated betonite (81.51 kg/m³ [28.6ppb]), kg/m³ [ppb]	10min	188.67 [66.2]	188.67 [66.2]	188.67 [66.2]
NaOH, 50%, kg/m³ [ppb]	30sec	8.55 [3.0]	8.55 [3.0]	8.55 [3.0]
KCl, kg/m³ [ppb]	2min	99.75 [35]	99.75 [35]	99.75 [35]
Tetrapolymer of AM/AMPS/AHPS/AA, kg/m³ [ppb]	10min	0	17.10 [6]	17.10 [6]
Poly(VP/AA), kg/m³ [ppb]	10min	6.27 [2.2]	5.70 [2.0]	5.70 [2.0]
Poly(maleate/allylsulfonate), 48%, kg/m³ [ppb]	5min	0	0	8.55 [3]
API Barite, kg/m³ [ppb]	10min	513.00 [180]	513.00 [180]	513.00 [180]
Aging Conditions		204.44°C [400F]/16hr hot rolling

Mud weight, kg/m³ [ppg]	1318.09 [11]			1318.09 [11]			1318.09 [11]
Fann data @48.89°C [120F]	BHR	AHR	R* (%)	BHR	AHR	R* (%)	BHR	AHR	R* (%)
600 rpm	80	57	71	85	70	82	95	83	87
300 rpm	64	40	63	65	57	88	75	59	79
200 rpm	57	36	63	57	50	88	67	47	70
100 rpm	50	32	64	46	40	87	54	33	61
6 rpm	24	16	67	22	18	82	27	15	55
3 rpm	18	15	83	20	15	75	24	13	54
10s gel, kg/m² [lb/100 ft²]	1.22 [25]	0.78 [16]	3.12 [64]	0.93 [19]	0.73 [15]	3.86 [79]	1.17 [24]	0.64 [13]	2.64 [54]
PV, mPas [cps]	24 [24]	17 [17]	71 [71]	20 [20]	13 [13]	65 [65]	20 [20]	24 [24]	120 [120]
YP, kg/m² [lb/100 ft²]	1.95 [40]	1.12 [23]	2.83 [58]	2.20 [45]	2.15 [44]	4.78 [98]	2.68 [55]	1.71 [35]	3.12 [64]
pH value	12.0	9.8	--	12.4	9.4	--	12.1	9.3	--

R*: Retention (%)

Table 5: Study of HT RM in 1917.22 kg/m³ [16ppg] drilling muds containing 99.75 kg/m³ [35ppb] KCl & 14.25 kg/m³ [5ppb] Bentonite

Composition	Mixing time	12443-63-1	12443-63-2	12443-63-3
Deionized water, bbl (ml)	--	177	177	177
Pre-hydrate API Non-treated betonite (53.01 kg/m³ [18.6ppb]), kg/m³ [ppb]	10min	188.67 [66.2]	188.67 [66.2]	188.67 [66.2]
NaOH, 50%, kg/m³ [ppb]	30sec	5.70 [2.0]	5.70 [2.0]	5.70 [2.0]
KCl, kg/m³ [ppb]	2min	99.75 [35]	99.75 [35]	99.75 [35]
Tetrapolymer of AM/AMPS/AHPS/AA, kg/m³ [ppb]	10min	0	17.10 [6]	17.10 [6]
Poly(VP/AA), kg/m³ [ppb]	10min	5.70 [2.0]	4.28 [1.5]	4.28 [1.5]
Poly(maleate/allylsulfonate), 48%, kg/m³ [ppb]	5min	0	0	11.40 [4]
API Barite, kg/m³ [ppb]	10min	940.50 [330]	940.50 [330]	940.50 [330]
Aging conditions		204.44°C [400F]/16hr hot rolling

Mud weight, kg/m³ [ppg]	1917.22 [16]			1917.22 [16]			1917.22 [16]
Fann data @48.89°C [120F]	BHR	AHR	R* (%)	BHR	AHR	R* (%)	BHR	AHR	R* (%)
600 rpm	250	83	33	115	78	68	168	64	38
300 rpm	240	72	29	80	60	75	140	47	34
200 rpm	235	68	29	70	55	79	127	40	31
100 rpm	215	60	28	58	45	78	108	32	29
6 rpm	110	34	31	37	20	54	60	16	27
3 rpm	100	31	31	34	18	53	45	15	33
10s gel, kg/m² [lb/100 ft²]	5.86 [120]	1.71 [35]	1.42 [29]	1.95 [40]	0.98 [20]	2.44 [50]	2.44 [50]	0.88 [18]	1.76 [36]
PV, mPas [cps]	10 [10]	11 [11]	110 [110]	35 [35]	18 [18]	51 [51]	28 [28]	17 [17]	61 [61]
YP, kg/m² [lb/100 ft²]	11.22 [230]	2.98 [61]	1.32 [27]	2.20 [45]	2.05 [42]	4.54 [93]	5.47 [112]	1.46 [30]	1.32 [27]
pH value	10	8.8	--	10.0	8.9	--	10.0	9.0	--

R*: Retention (%)

Claims

A stable water based High-Temperature-High-Pressure (HTHP) and/or Non-HTHP copolymer for oil and gas applications consisting of
(i) a linear poly (vinyl amide/polymerizable carboxylic acid) copolymer, having a composition, by weight, of 25-75 wt. % of a vinyl amide monomer selected from vinyl pyrrolidone, vinyl caprolactam, N-vinyl-N-methylacetamide and mixtures thereof, and 25-75 wt. % of a polymerizable carboxylic acid monomer selected from acrylic acid, (meth)acrylic acid, crotonic acid, itaconic acid, maleic acid and mixture thereof; and

(ii) a crosslinker in an amount of 0.01-5% based on weight of total monomers, wherein said crosslinker for crosslinking the copolymer according to item (i) has at least two free radical polymerizable groups in the molecule and is selected from the group consisting of Divinylimidazolidone (DVI), N,N',N"-triallyl-triazine-trione, Methyene-bis-acryamide, Methylene-bis-(meth)acrylamide, Triallyl amine, Triallylglucose, Ethyleneglycol-di-(meth)acrylate, Diethyleneglycol-di-(meth)acrylate, Triethyleneglycol-di-(meth)acrylate, Tetraethyleneglycol-di-(meth)acrylate, Polyethyleneglycol-di-(meth)acrylate, Pentaerythritol-di-allylether, Pentaerythritol-di-(meth)acrylate, Pentaerythritol tri(meth)acrylate, Pentaerythritol-tetra-(meth)acrylate, 1-vinyl-3-(E)-ethylidene-pyrrolidone (EVP), Allyl methacrylamide, allyl glycidyl ether, glycidyl acrylate, hydroxyacrylamide and/or Divinylbenzene.
The copolymer according to claim 1, wherein the copolymer is characterized by an aqueous solution having a viscosity in a range of 30000 to 90000 mPas (30,000 to 90,000 cps) at a pH of 9 and wherein, the Brookfield RVT, T-bar C @10 RPM, 60 sec, 1% resin solids in water.
The copolymer according to claim 1 or 2, wherein said vinyl amide is vinyl pyrrolidone.
The copolymer according to claim 1 or 2, wherein said polymerizable carboxylic acid is acrylic acid (AA).
The copolymer according to claim 1, wherein the copolymer is prepared by precipitation polymerization, reverse emulsion polymerization, liquid dispersion polymerization, gel polymerization, dispersion polymerization, solution polymerization, suspension polymerization, or bulk polymerization.
Use of the copolymer according to any of the claims 1 to 5 in oil and gas applications as rheology modifier/thickener/suspension agent for drilling/drill-in/packer fluids, cementing viscosifier, friction reducer in lime/fresh-water/brine based drilling, friction reducer in oil-well fracturing, shale swell inhibitor/clay stabilizer, fluid loss additive, viscosifier in fresh-water/seawater/saline based drilling fluids, filtration control, viscosifier for oil-well stimulation, drilling-aids for oil/water/geological drillings, completion fluids and work-over fluids, invert-drilling fluids, and/or polymer flooding for enhanced oil recovery.
A stable water based High-Temperature-High-Pressure (HTHP) and/or Non-HTHP drilling fluid composition, the composition being suitable for use under High-Temperature-High-Pressure (HTHP) referring to a well having an undisturbed bottom-hole temperature of greater than 148.89 °C (300 °F) and a bottom-hole pressure of at least 34.47 MPa (5000 psi), comprising:
i. fresh water and/or brine solution as base fluids;

ii. 1.43 kg/m³ (0.5 ppb) to 28.50 kg/m³ (10 ppb) of crosslinked copolymer consisting of (i) a linear poly(vinyl amide/polymerizable carboxylic acid) copolymer, having a composition, by weight, of 25-75 wt. % of a vinyl amide monomer selected from vinyl pyrrolidone, vinyl caprolactam, N-vinyl-N-methylacetamide and mixtures thereof, and 25-75 wt. % of a polymerizable carboxylic acid monomer selected from acrylic acid, (meth)acrylic acid, crotonic acid, itaconic acid, maleic acid and mixture thereof; and (ii) a crosslinker in an amount of 0.01-5% based on weight of total monomers as rheology modifier and for crosslinking the copolymer according to item (i);

iii. 0 ppb to 57.00 kg/m³ (20 ppb) of a dual-functional polymer functioning as Rheology Modifiers and/or Fluid Loss Additives (FLA);

iv. 0 ppb to 71.25 kg/m³ (25 ppb) of HTHP or non-HTHP based Fluid Loss Additives (FLA);

v. 228.00 kg/m³ (80 ppb) to 1140.00 kg/m³ (400 ppb) of weighting agents;

vi. optionally 0 ppb to 85.50 kg/m³ (30 ppb) of drilling solids; and

vii. optionally 0 ppb to 85.50 kg/m³ (30 ppb) of at least one dispersing agent.
The water based drilling fluid composition according to claim 7, wherein said dual-functional polymer which is functioning as Rheology Modifiers and/or Fluid Loss Additives (FLA), is selected from the group consisting of a polymer obtained by polymerizing
(i) an acrylamide (AM) or a substituted acrylamide selected from the group consisting of N-methacrylamide, N-isopropylacrylamide, N-butylacrylamide, N,N-dimethylacrylamide, or N-hydroxymethylacrylamide;

(ii) a monomer containing sulfonate functionality which is 2-acrylamido-2-methylpropanesulfonic acid (AMPS);

(iii) a substituted allyl alkylene ether compound selected from the group consisting of 3-allyloxy-hydroxy-propanephosphate, 3-allyloxy-hydroxy-propanesulfonate, and 3-allyloxy-hydroxy-propanephosphite; and,

(iv) a monomer containing carboxylic acid functionality selected from the group consisting of acrylic acid, methacrylic acid, maleic acid or anhydride, itaconic acid, crotonic acid, fumaric acid, and citraconic acid; and a crosslinker in an amount of 0.1-5% based on weight of total monomers.
The water based drilling fluid composition of claim 8, wherein said dual-functional polymer is a crosslinked tetrapolymer of (i) an acrylamide (AM); 2-acrylamido-2-methylpropanesulfonic acid (AMPS); (iii) 3-allyloxy-hydroxy-propanesulfonate (AHPS); and, (iv) acrylic acid (AA); and wherein, N, N-methylene-bis-acrylamide is a crosslinker.
The water based drilling fluid composition according to claim 7, wherein said weighting agent is selected from the group consisting of barite, hematite, manganese oxide, iron oxide, sized calcium carbonate, magnesium carbonate, aqueous soluble organic and inorganic salts and mixtures thereof.
The water based drilling fluid composition according to claim 7 suitable for high-temperature high-pressure (HTHP) drilling operations having a temperature of above 148.89 °C (300 °F).
The water based drilling fluid composition according to claim 7 suitable for Non-HTHP drilling operations having a temperature of ambient to 121.11 °C (250 °F).
The water based drilling fluid composition according of claim 7 having a pH in the range of from 6.0 to 13.0.
A stable water based High-Temperature High-Pressure (HTHP) and/or Non-HTHP completion fluid composition, having a density of 994.56 to 2516.35 kg/m³ (8.3 to 21.0 ppg), comprising:
i. brine based fluids;

ii. 1.43 kg/m³ (0.5 ppb) to 28.50 kg/m³ (10 ppb) of crosslinked copolymer of claim 1 as rheology modifier;

iii. optionally 0 to 71.25 kg/m³ (25 ppb) of the dual-functional polymer of claim 8; and

iv. optionally 14.25 kg/m³ (5 ppb) to 285.00 kg/m³ (100 ppb) bridging agent.
A stable water based High-Temperature High-Pressure (HTHP) and/or Non-HTHP drill-in fluids composition, having a density of 994.56 to 2516.35 kg/m³ (8.3 to 21.0 ppg), comprising:
i. brine based fluids;

ii. 1.43 kg/m³ (0.5 ppb) to 28.50 kg/m³ (10 ppb) of the crosslinked copolymer of claim 1 as rheology modifiers;

iii. optionally 0 to 71.25 kg/m³ (25 ppb) of the dual-functional polymer of claim 8;

iv. 0 ppb to 71.25 kg/m³ (25 ppb) of HTHP or non-HTHP based Fluid Loss Additives (FLA); and

v. 14.25 kg/m³ (5 ppb) to 285.00 kg/m³ (100 ppb) of bridging agents are selected from CaCO₃ or sized salts.